The present invention relates generally to a novel construction for an improved welding apparatus, and more specifically to a novel construction for an improved electric arc welding gun/torch.
Welding processes are widely used in modem day manufacturing. One such welding process is commonly referred to as arc welding, which utilizes an electrical current, and an electrode. The American Welding Society ("AWS") defines arc welding with seven subclasses, viz. shielded metal arc welding, submerged arc welding, gas metal arc welding, flux cored arc welding, gas tungsten arc welding, plasma arc welding, and electroslag welding. Electrical current heats the tip of an electrode such that the electrode and the adjacent portions of the workpiece become hot enough to fuse. In order to prevent molten metal from reacting with components of the surrounding ambient atmosphere, a fluid flow of a shielding gas, such as helium, argon and the like, or a solid slag surrounds the molten metal and the adjacent portions of the workpiece.
In some instances, these things needed for arc welding are provided in the form of a welding apparatus or gun which facilitates manipulation of the electrode and the shield by a workman during welding. One example of an arc welding gun of the prior art generally comprises a handle member connected to an end of a composite cable which delivers arc power and shielding gas from suitable sources. A cone nut is located at the end of the composite cable, and the cone nut has threads connectable with complementary threads on an end fitting. The end fitting has another set of threads which are engagable with complementary threads on a lock nut for operatively connecting a body tube to the end fitting. Because the end fitting and the body tube are electrically conductive, an insulating member may be positioned over exposed portions of the end fitting and the lock nut. A liner, in which a consumable electrode can be inserted, extends through the composite cable and the body tube, and terminates adjacent a distal end of the body tube. A contact tip for weldingly contacting the electrode is disposed at the distal end of the body tube.
Currents used in arc welding can be on the order of hundreds of Amps. These currents generate sufficient heat, especially at and adjacent the contact tip, which, in combination with other effects of arc welding, can cause deterioration of portions of the welding gun. The body tube and the liner are often susceptible to this deterioration. In addition, body tubes may have certain, predetermined configurations which make them particularly adept at forming a certain weld, may have particular utility with a given workpiece, etc. The liner may be abraded within the body tube as the electrode is continuously used. Therefore, it may become desirable to replace the body tube and/or the liner in order to insure efficient welding of the workpiece. However, the method of replacing a body tube and/or a liner may be quite difficult or tedious and may be relatively expensive in time and in labor.
A typical method of replacing a body tube A may be more easily understood with reference to FIG. 2. To replace a body tube A, the handle member must be removed. The insulating member is slid off of the lock nut B and the end fitting C to reveal the driving flats of both elements. The cone nut D at the end of the composite cable E is inserted into a vise F, and the vise F is activated to firmly hold the cone nut D against rotation. Now, a first wrench is applied to the lock nut B to rotate the lock nut B with respect to the end fitting C to disengage the threaded connection therebetween. A second wrench is applied to the end fitting C to fix the end fitting C against rotation with respect to the cone nut D or the lock nut B. Force is applied to the first wrench to rotate the lock nut B while another force is applied to the second wrench to hold the end fitting C fixed. This force application continues or is increased until the threaded connection between the lock nut B and the end firing C is loosened. Once the connection is loosened, the body tube A is rotated with the lock nut B and removed completely from the end fitting E.
Because the threaded connection between the lock nut B and the end fitting C is torqued, often to about 15 foot-pounds, the forces required to break the threaded connection may be rather significant. In addition, appropriate portions of the body tube A and/or the end fitting C may be tapered at a slight incline. This taper may make the time required to disassemble the body tube A and the end fitting C rather long, which increases the down time of the welding gun, and which possibly correspondingly decreases the amount of revenues that can be generated by use of the gun. Alternatively, two workmen, one working each of the wrenches, may cooperate to loosen the connection, but this method is relatively labor intensive, thereby also possibly decreasing associated revenues.
The liner extends through the axial length of the composite cable E and into the body tube A. The liner may be ten to fifteen feet long or longer depending upon the length of the composite cable E desired for a specific welding application. While the old liner may be relatively easily removed by pulling it through the open, distal end of the composite cable connection, the new liner will have to be carefully inserted through the entire length of the composite cable E. This installation process may be tedious, requires removal of the welding gun from production, possibly further reducing revenues. In addition, it is to be noted that the operative welding temperatures, about 400 degrees Fahrenheit, tend to be concentrated at the contact tip of the welding gun. Thus, significant deterioration of the liner may only occur immediately adjacent the contact tip. This means that, in some instances, deterioration of a few inches of the liner may require replacement of the entire liner, which may be almost an order of magnitude longer than the deteriorated portion of the liner. Because the entire liner must be replaced due to deterioration of such a small portion thereof, liner replacement of the present art can be wasteful and also costly. These things can increase the costs of maintaining and/or using a welding gun because of increased labor and parts costs.
Because of these characteristics, among others, of some prior art welding apparatuses, such as arc welding guns and the like, it is desirable to provide an improved welding apparatus which is not subject to some, if not all of the above-discussed characteristics of the prior art welding guns. The present invention is intended to provide such an improvement.